Multi-Step Form Data

[eluser]BrandonDurham[/eluser]
When creating a multi-step form (specifically a form broken up into three steps/pages) is it a bad idea to create a session variable containing the form data to carry it between pages?

I'm working on a form for a CMS where the user can add new albums and all related info (images, tracks, mp3s, etc.) and I've broken it down into three steps. I want them to be able to move freely between all three steps, and this is why I'm interested in adding the info to a session variable instead of filling in hidden form fields with the $_POST data since they may not always land on each step via a POST.

Is this bad form (no pun intended)? Is it unsafe (the whole CMS is protected with user authentication)?

I appreciate any help I can get. Thanks!